Structure of Rhizobium sp. 4-9 histamine dehydrogenase and analysis of the electron transfer pathway to an abiological electron acceptor

• Published in: Archives of biochemistry and biophysics 2023-07, Vol.742, p.109612-109612, Article 109612
• Main Authors: Goyal, Priyanka, Deay, Dwight, Seibold, Steve, Candido, A.C.L., Lovell, Scott, Battaile, Kevin P., Wilson, George S., Richter, Mark L., Petillo, Peter A.
• Format: Article
• Language: English
• Subjects: Crystal structure; Electron transfer; Electron Transport; Electrons; Ferricenium; Flavoprotein; Histamine; Metallocenes; Oxidants; Protein engineering; Rhizobium; Rhizobium sp. 4-9 histamine dehydrogenase
• ISSN: 0003-9861; 1096-0384
• DOI: 10.1016/j.abb.2023.109612

Histamine dehydrogenase from the gram-negative bacterium Rhizobium sp. 4-9 (HaDHR) is a member of a small family of dehydrogenases containing a covalently attached FMN, and the only member so far identified to date that does not exhibit substrate inhibition. In this study, we present the 2.1 Å resolution crystal structure of HaDHR. This new structure allowed for the identification of the internal electron transfer pathway to abiological ferrocene-based mediators. Alanine 437 was identified as the exit point of electrons from the Fe4S4 cluster. The enzyme was modified with a Ser436Cys mutation to facilitate covalent attachment of a ferrocene moiety. When modified with Fc-maleimide, this new construct demonstrated direct electron transfer from the enzyme to a gold electrode in a histamine concentration-dependent manner without the need for any additional electron mediators. [Display omitted] •The crystal structure for Histamine dehydrogenase from Rhizobium sp. 4-9 is described.•The electron transfer pathway from the active site to the surface of the protein is delineated.•Attachment of an abiological electron acceptor successfully captures electrons.•The modified protein undergoes direct electron transfer to an electrode surface.